Zigzag antenna



Jan. 25, 1966 KlYOSHl NAGA] 3,231,894

ZIGZAG ANTENNA Filed June 21. 1961 2 Sheets-Sheet 1 Imzeni'cu:

Kl'goslu Nagaj United States Patent 3,231,894 ZIGZAG ANTENNA Kiyoshi Nagai, Sendai-shi, Miyagi-ken, Japan, assignor to Sony Corporation,Tokyo, Japan, a corporation of Japan Filed June 21, 1961, Ser. No.118,615 Claims priority, application Japan, June 23, 1960,

35/ 29,211 3 Claims. (Cl. 343-806) This inventionrelates to antennasand, more particularly, to a zigzag antenna quencies.

One object of this invention is to provide a zigzag antenna which isrelatively short in length and effective in operation.

A further object of this invention is to provide a zigzag antenna havinga pair of antenna elements which are formed by printing a zigzagconductive layer on a base plate.

An antenna constructed in accordance with the invention and designed tooperate over a given range of frequencies comprises a base plate havingfirst and second flat surfaces on opposite sides. First and secondantenna elements are fastened to the firstside of the base plate andthird and fourth antenna elements are fastened to the second side of thebase plate. Each of the first and second antenna elements has an inputend substantially at the center of the first side and are folded ingenerally zigzag fashion in the direction of the opposite ends of thebase plate. The third and fourth antenna elements have input ends atsubstantially the center of the base plate and are folded in thedirection of the opposite ends of the 'base plate. The outer ends of thefirst and third antenna elements are connected together and the outerends of the second and fourthantenna elements are connected together.The input ends of the third and fourth elements are all connectedtogether.

Other objects,'features and advantages of this invention will becomefully apparent from the following detailed description taken inconnection with the accompanying figures of the drawings, in which:

FIGURE 1 is a schematic diagram illustrating an antenna construction;

FIGURE 2 is a perspective view of another antenna structure wherein theantenna elements are applied to a base plate; a i t FIGURES 3 and 4illustrate schematically variations of the antenna shown in FIGURE l; ii t FIGURE 5 illustrates a folded zigzag antenna constructed inaccordance with this invention;

FIGURE 6 includes curves showing some characteristics of a zigzagantenna constructed in accordance with this invention;

FIGURE 7 includes curves showing other characteristics of an antennaconstructed in accordance with this invention; and

FIGURE 8 shows some characteristics of the antenna illustrated in FIGURE5.

Referring now to FIG. 1, on substantially the same plane is provided apair of antenna elements 1a and 1b which are formed by foldingconductive wires in zigzag fashion, and which are arranged opposite toeach other in the advance direction of folding. The inner ends 2a and 2bof the elements 1a and 1b, respectively, are feeding points while theouter ends 3a and 3b are open circuited. The portion of each antennaelement between the two ends is folded in one plane to give it a heightD and a length L. The length L of the zigzag antenna elements In and 1band the height D are made substantially less than M4, i. being the wavelength of an 3,231,894 Patented Jan. 25, 1966 electromagneticwave at apredetermined frequency within a range of frequencies for which theantenna is de signed.

The antenna elements may be composed of a conductive wire, conductiveplate or conductive pipe, but it may preferably be constructed of aconductive layer 5 on a base plate 4 of an insulating material such asBakelite or the like. The print wiring has a predetermined width d asshown in FIGURE 2. Thus both antenna elements for use at short wave fre-1a and 1b may easily be arranged on substantially the same plane.

The shape of the antenna elements may be made either in a sawtooth formhaving a sharp triangular top as shown in FIGURE 3 or a sawtooth formhaving a flat top as shown in FIGURE 4.

, FIGURE 5 shows another form of an antenna wherein two antenna elementsIn and 1b are also arranged on the back face of the insulation baseplate 4 along with the front pair of the antenna elements 1a and 1b. Thetwo outer ends 3a and 3a are connected together by a conducting strip 6aand the two ends 3b and 3b are connected together by a strip 6b. Theinner ends of the two elements 1a and 1b are connected together by astrip 60.

When an antenna element folded zigzag in the manner described above isused, a zero phase current is distributed on it, so that the length fromtrough to trough of the current distribution is shortened. That is, justwhen the zero phase current of M2 gets on the antenna elements 1a and 1balong the zigzag direction, the wavelength is much diminished orcontracted; on the other hand, the phase velocity along the antennaelements be comes higher so that the wave length is extended. When usinga zigzag antenna having a resonant frequency in the range of about tomegacycles in which the print wiring is eifected on the insulation baseplate 4 as shown in FIGURE 2, and D is 5 cm. and L is 20 cm., as shownin FIGURE 2, the rates of extension and contraction are shown by curves7 and 8, respectively, in FIGURE 6. The abscissa indicates the intervalbetween adjacent antenna elements, namely the pitch W and the ordinateindicates the rates of contraction and extension in percentage.

The input impedance and the standing wave ratio characteristics when thepitch W is 2 mm. are shown in FIGURE 7. In this figure, the abscissa isthe frequency f in megacycles and the ordinate is the equivalent inputseries resistance R, the equivalent series reactance component X and thestanding wave ratio SWR with a load resistance of 100 ohms. Theresistance R, the reactive impedance X, and the standing wave ratio areshown by curves 9, 10 and 11 respectively. It is apparent from thesecurves that the characteristic of this antenna are similar to that of adipole antenna made of a metal rod of /2 In the case of a folded antennaof the type shown in FIGURE 5, wherein the height D is 5 cm., length Lis 20 cm. and the pitch W of the zigzag antenna is 2 mm., and the printwiring is effected on both faces of the base plate 4, itscharacteristics are shown by the curves in FIGURE 8 when the antennaelements 1a, 1b, 1a and 1b are short circuited in such a way that theentire length of the complete antenna is cm. In this figure, theabscissa is expressed in frequency f in megacycles, the ordinate is theequivalent input series resistance R, the equivalent series reactance X,and the standing Wave ratio with a load resistance of 100 ohms; theseare shown by curves 12, 13 and 14, respectively. It is apparent fromthese figures that the characteristic of this antenna is similar to thatof the folded dipole antenna and the standing wave ratio is kept within6 over the range from 100 to 140 megacycles, which presents a veryexcellent characteristic.

The above description has been made mainly in connection with anembodiment wherein the antenna elements are arranged on the print baseplate 4 and have the configuration shown in FIGURE 4, but by varying itsshape properly, many types of antennas having various characteristicsmay be produced. Furthermore, if the print base, on both sides of whichthe zigzag antenna elements can be composed, is employed, it can be massproduced at a lower price. The antenna may be provided with the desiredpositive phase transmission characteristic, so that antennas applicableto various uses may easily be manufactured. By applying a dielectric, amagnetic substance or the like as the material of the print plate, theantenna can be reduced in size, and a particular antenna may be madethereby. It is of course desirable to use the print base plate for thepurpose of making the antenna strong. In the case of the folded antenna,a variable frequency type antenna may be constructed by changing theshort circuit point of the positive-phase current. In other words, theelements 1a and 1a, and the elements 1b and 1b, can be connectedtogether at a point closer to the feed point 2a by a suitable jumper.

It will be apparent that modifications and variations may be effectedwithout departing from the scope of the novel concepts of thisinvention.

I claim as my invention:

1. An antenna structure designed to operate over a given range offrequencies comprising a base plate having first and second fiatsurfaces on opposing sides of said base plate, first and second antennaelements fastened to said first side of said base plate and third andfourth antenna elements fastened to said second side of said base plate,each of said first and second antenna elements having an input end atsubstantially the center of said first side and being folded in zigzagfashion in the direction of opposite ends of said base plate, said thirdand fourth antenna elements having input ends at substantially thecenter of said base plate and being folded in the direction of saidopposite ends of said base plate, the outer ends of said first and thirdantenna elements being connected together and the outer ends of saidsecond and fourth antenna elements being connected together, and theinput ends of said third and fourth antenna elements being connectedtogether.

2. An antenna structure designed to operate over a given range offrequencies comprising a base plate having first and second fiatsurfaces on opposing sides of said base plate, first and second antennaelements fastened in printed circuit fashion to said first side of saidbase plate and third and fourth antenna elements fastened in printedcircuit fashion to said second side of said base plate, each of saidfirst and second antenna elements having an input end substantially atthe center of said first side and being folded in zigzag fashion in thedirection of opposite ends of said base plate, said third and fourthantenna elements having input ends at substantially the center of saidbase plate and being folded in the direction of said opposite ends ofsaid base plate, the outer ends of said first and third antenna elementsbeing connected together and the outer ends of said second and fourthantenna elements being connected together, and the input ends of saidthird and fourth antenna elements being connected together.

3. An antenna structure designed to operate over a given range offrequencies comprising a base plate of insulating material having firstand second flat surfaces on opposing sides of said base plate, first andsecond antenna elements fastened in printed circuit fashion to saidfirst side of said base plate and third and fourth antenna elementsfastened in printed circuit fashion to said second side of said baseplate with the height and length of each of said antenna elements beingless than one fourth of a wave length over said given range offrequencies, each of said first and second antenna elements having aninput end substantially at the center of said first side and beingfolded in zigzag fashion in the direction of opposite ends of said baseplate, said third and fourth antenna elements having input ends atsubstantially the center of said base plate and being folded in thedirection of said opposite ends of said base plate, the outer ends ofsaid first and third antenna elements being connected together and theouter ends of said second and fourth antenna elements being connectedtogether, and the input ends of said third and fourth antenna elementsbeing connected together.

References Cited by the Examiner UNITED STATES PATENTS 2,412,249 12/1946Brown et al. 343705 2,472,106 6/ 1949 Hansen 343--824 2,990,547 6/1961McDougal 343--908 X 3,013,268 12/1961 Du Hamel et al. 343908 X 3,020,5502/ 1962 Beever 343-795 FOREIGN PATENTS 533,153 11/1954 Belgium.

864,707 1/ 3 Germany. 1,019,717 11/1957 Germany.

743,794 1/ 1956 Great Britain.

244,731 5/ 1947 Switzerland.

HERMAN KARL SAALBACH, Primary Examiner.

ELI LIEBERMAN, Examiner.

1. AN ANTENNA STRUCTURE DESIGNED TO OPERATE OVER A GIVEN RANGE OFFREQUENCIES COMPRISING A BASE PLATE HAVING FIRST AND SECOND SURFACES ONOPPOSITE SIDES OF SAID BASE PLATE, FIRST AND SECOND ANTENNA ELEMENTSFASTENED TO SAID FIRST SIDE OF SAID BASE PLATE AND THIRD AND FOURTHANTENNA ELEMENTS FASTENED TO SAID SECOND SIDE OF SAID BASE PLATE, EACHOF SAID FIRST AND SECOND ANTENNA ELEMENTS HAVING AN INPUT END ATSUBSTANTIALLY THE CENTER OF SAID FIRST SIDE AND BEING FOLDED IN ZIGZAGFASHION IN THE DIRECTION OF OPPOSITE ENDS OF SAID BASE PLATE, SAID THIRDAND FOURTH